The Romance of Modern Chemistry

NATURE’S BUILDING MATERIAL which combine with a definite weight of the first element are as one to two, or two to three—some simple ratio of that sort These remarkable facts about the proportions in which the elements combine were discovered soon after the balance had become part of the regular equipment of a laboratory, and chemists began to cast about for an explanation. The result was that they came to regard matter as made up of separate particles of extremely small size called molecules, which were incapable of further division except by chemical means. A fragment of iron, if magnified sufficiently, would thus resemble a heap of cannon balls, each cannon ball representing a molecule. It must be remembered, of course, that this is only a theory, a picture, for nobody has ever divided matter so finely that further division was impossible; a single separate molecule has never been picked out; indeed, it must be much smaller than anything that has ever been seen, even under the most powerful microscope. Although the molecule of a substance is the smallest particle of that substance which can exist by itself, it is possible to break it up by chemical means. The chemist’s experiments have led him to believe that a molecule consists of so-called atoms, sometimes all of one kind, sometimes of different kinds. When the atoms in a mole- cule are all of the same kind, it is an element which we are considering; when the atoms are of different kinds, it is a compound. To separate the atoms which are present together in any one molecule, we bring another kind of molecule, with different atoms, alongside. In a great many cases the atoms will promptly change partners, and new molecules—that is, new substances—are produced. Suppose, for example, we bring together a molecule AB,